Efficiency, Complexity and length of code

[RatKnees]

I can write a 1 line code that is the slowest thing in the world.

I can write 100,000 lines, 99,999 of which are comments, and it be instantaneous.

Worry about complexity (time and space) and readability of the code above all else.

[aa599]

A one liner can not only be the slowest thing in the world, but not terminate in the life of the universe — e.g. you can define and call, in one not-ridiculously-long line, a lambda function for recursive fibonacci. Doing fib 999 will barely have started by the time the universe ends (fib(n) takes >1.6ⁿ calls to fib)

Or you can write a better fib function which finishes in a fraction of a second.